Assembling the Telescope

We have now been here in Antarctica for about a week, and it is time to give you an update on our X-Calibur activities. Last week, we checked out the detector. We verified that it is still working after it spent the last four months in a shipping container. All readout ASICs are still working and the electronic noise levels are acceptable, which is one of our main concerns. In parallel, our colleagues from SuperTIGER checked out their instrument. We are sharing a payload building with them and their instrument is very close to flight readiness. The SuperTIGER team was unfortunate enough to spend an entire summer in Antarctica last year without a chance to launch. So they left their instrument in McMurdo and returned this season.

X-Calibur in its anticoincidence shield on the left and the control computers to the right.

Today was an important day for us, as we were able to assemble the telescope truss and the balloon gondola. In order to do so, the CSBF crew had to move SuperTIGER out of the building for a few hours in order to make room for us to move in. First, the gondola was moved out of its container and hoisted into the building. Then the CSBF rigging crew unloaded the telescope truss structures and hand carried them into the building. Installation of the trusses onto the center frame went very smoothly since we had done that several times before. The work took under 2 hours. We also installed the detector onto the telescope truss. At the end of the day, most of the mechanical work was completed, although we still have about half a day of work on the gondola ahead of us. Today was a very successful day. Next, we’ll concentrate on the electronics.

Loading the gondola into the payload building.

Attaching the rear half of the telescope truss to the gondola.

The gondola, both trusses, and the detector have been assembled.


  1. Sybille says:

    Interesting and love the pictures, but wonder what an anticoincidence shield is?

    • Fabian Kislat says:

      Hi Sybille, Thanks for the question. I’m glad you like the pictures. Our detector not only detects X-rays from the astrophysical object we’re interested in, but also cosmic rays and gamma-rays caused by interactions of cosmic rays in the Earths atmosphere. These particles constitute a background to our observations and reduce the statistical significance of the signal. They enter the detector from all directions. In order to suppress this background and enhance our signal-to-background ratio, we do two things: first we surround our detector with absorbing material on all sides with only a small opening at the front where the X-rays from the source of interest enter the detector. The second thing we do, is to make some of this absorber out of a material that acts as a particle detector, a so called scintillator. When one of the background particles interacts in this detector material, it creates a small flash of light that we detect with sensitive light sensors called photomultiplier tubes. When such a flash of light is registered at the same time as a signal in one of our detectors, we reject that signal since it is most likely due to a background particle that made it through the absorbing material. We call that logic an anticoincidence and the detector surrounding our X-ray detector the “anticoincidence shield” as it uses the anticoincidence logic to shield us from background particles.

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